It has been our experience that those with traumatic injuries often report pain in the head, face, eyes, ears and mouth (such as chronic headaches, or trigeminal neuralgia) as more severe, more debilitating, more disruptive and more emotionally draining than pain anywhere else in the body. A recent study reveals that the brain’s wiring correlates with these types of pain complaints from head and face pain.
Published in Nature Neuroscience on November 13, 2017[1], the Duke University research team found that sensory neurons carrying pain signals from the head to the brain are more sensitive to pain than neurons carrying pain signals from the body. Sensory neurons from the head and face are wired directly into one of the brain’s principal emotional signaling hubs, the parabrachial nucleus (PBL). The PBL is a region that is directly wired into the brain’s instinctive and emotional centers. Pain in the head or face directly stimulates PBL neurons.
The Duke University team examined the neural circuitry underlying head/face pain vs. body pain by tracking brain activity in mice after irritating the paw or the face. They found that irritating the face led to higher activity in the brain’s PBL. The team was then able to pinpoint the sources of neurons that caused this elevated PBL activity, using their own activity-dependent technology called CANE, allowing them to perform comprehensive anatomical input-output mapping. The result: a monosynaptic connection between cranial sensory neurons and the PBL nociceptive neurons. Senior author and neurobiologist Fan Wang explained, “It was a Eureka moment because the body neurons only have this indirect pathway to the PBL, whereas the head and face neurons, in addition to this indirect pathway, also have a direct input.”
Not only does the study suggest that the neurons are more sensitive to pain in the head, but people report higher levels of fear and emotional suffering in response to head/face pain vs. body pain. The study confirmed these higher levels of fear and suffering by functional MRI, which showed greater activity in the region of the brain involved in emotional experiences, the amygdala, in response to head pain vs. body pain.
Co-author and professor of neurologist Wolfgang Liedtke explained, “We have the first biological explanation for why this type of pain can be so much more emotionally taxing than others.” Professor of neurobiology Qiufu Ma of Harvard Medical School, who was not involved in this study, said, “The discovery of this direct pain pathway might provide an explanation why facial pain is more severe and more unpleasant.”[2]
The study can ultimately impact how specialists effectively treat pain mediated by the craniofacial nerve, such as treatment options for chronic headaches and neuropathic facial pain. This study and future studies will open the door toward a better understanding of chronic head and face pain, and promote more effective treatment options that will benefit those suffering from head and face pain.
The attorneys at Adler Giersch are dedicated to studying the developments in medicine and research as it relates to finding relief for people suffering from brain injury and/or chronic pain due to head and face trauma. Consultations are complimentary and confidential. Simply give us a call at 206.682.0300 or send an email to [email protected].
[1] “A Craniofacial-Specific Monosynaptic Circuit Enables Heightened Affective Pain,” Erica Rodriguez, Katsuyasu Sakurai, Jennie Xu, Yong Chen, Koji Toda, Shengli Zhao, Bao-Xia Han, David Ryu, Henry Yin, Wolfgang Liedtke and Fan Wan. Nature Neuroscience, Nov. 13, 2017. DOI: 10.1038/s41593-017-0012-1
[2] https://today.duke.edu/2017/11/why-head-and-face-pain-causes-more-suffering
